title: Influence of genomic G+C content on average amino-acid composition of proteins from 59 bacterial species.
abstract: The amino-acid composition of 23,490 proteins from 59 bacterial species was analyzed as a function of genomic G+C content. Observed amino-acid frequencies were compared with those expected from a neutral model assuming the absence of selection on average protein composition. Integral membrane proteins and non-integral membrane proteins were analyzed separately. The average deviation from this neutral model shows that there is a selective pressure increasing content in charged amino acids for non-integral membrane proteins, and content in hydrophobic amino acids for integral membrane proteins. Amino-acid frequencies were greatly influenced by genomic G+C content, but the influence was found to be often weaker than predicted. This may be evidence for a selective pressure, maintaining most amino-acid frequencies close to an optimal value. Concordance between the genetic code and protein composition is discussed in the light of this observation.
authors.affiliation: CNRS UMR 5558-Laboratoire BGBP, Université Claude Bernard, Villeurbanne, France. lobry@biomserv.univ-lyon1.fr
authors.forename: J R
authors.initials: JR
authors.lastname: Lobry
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D001426:Bacterial Proteins / Q000737:chemistry*; D003596:Cytosine / Q000032:analysis*; D016680:Genome, Bacterial; D006147:Guanine / Q000032:analysis*
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D006147:Guanine; D003596:Cytosine